For the transmission of luminous signals over long distances, such an optical cable must be made up from two or more portions properly interconnected to provide the necessary optical and mechanical continuity. Such interconnection requires the individual splicing of pairs of fiber sections from respective cable portions, with preliminary stripping of the usual protective sheath from the light-conducting core of each fiber section in the vicinity of its free end. Generally, however, the bare fiber extremity has little mechanical strength so as to be susceptible to rupture under stress; this is true even if the interconnected fiber ends are again covered by a protective layer.
It is therefore not practical to connect such fiber sections by simply inserting their bare extremities from opposite ends into a coupling sleeve in accordance with conventional techniques.
In a multifiber cable, moreover, it is often important to equalize the lengths of the light paths constituted by the several fibers in order to prevent a relative dephasing of the signals conveyed thereby. With straight-line fiber sections spliced in the aforementioned manner, subsequently detected phase differences may be difficult to correct.